People say 200$/kg just with booster reuse, and 20$/kg with full reuse. Of course this might be too optimistic, but I truly believe we might reach under 50$ in this decade.
There is a lot of possibilities to make a trip to the moon cheaper though. If we make LEO that cheap, we can build a lot of infrastructure in the space that would make the tourism to moon more affordable. Like keeping a few starships always in orbit as some kind of space-hotel-metro system.
This will probably take a few more decades, though.
On the civilian side, SpaceX saved NASA $2 billion for just one payload, Europa Clipper <https://arstechnica.com/space/2023/10/a-year-from-launch-the...>, so who knows how many billions more from other launches.
All we can say is under $1,000/kg. Which is conservative, that limit being about two thirds that of Falcon Heavy’s theoretical cost to LEO in a reüsable configuration.